. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. DENISON: THE CYATHASPIDIDAE 333. Fig. 101. Transverse sections through dermal shields of Irregulareaspidinae and Ctenaspidinae (X 50). A, Dikenaspis yukonensis, CNHM, slide 4037; B, Ir- regidareaspis sp., CNHM, slide 4591; C, Ctenaspis dentata, CNHM, slide 4049. bl, basal layer; ca, chamber of cancellous layer; cc2, canal connecting pulp canal to intercostal groove; dr, dentine ridge; dru large, elevated dentine ridge; ig, intercostal groove; pc, pulp canal; rl, reticular layer; tb, tubercle; x, line o
. The Cyathaspididae; a family of Silurian and Devonian jawless vertebrates. Cyathaspididae. DENISON: THE CYATHASPIDIDAE 333. Fig. 101. Transverse sections through dermal shields of Irregulareaspidinae and Ctenaspidinae (X 50). A, Dikenaspis yukonensis, CNHM, slide 4037; B, Ir- regidareaspis sp., CNHM, slide 4591; C, Ctenaspis dentata, CNHM, slide 4049. bl, basal layer; ca, chamber of cancellous layer; cc2, canal connecting pulp canal to intercostal groove; dr, dentine ridge; dru large, elevated dentine ridge; ig, intercostal groove; pc, pulp canal; rl, reticular layer; tb, tubercle; x, line of meeting of central and lateral epitega. canal. The tubules are generally somewhat irregular, and branch one or more times between the pulp canal and their termination near the surface. The surface of a ridge sometimes has a thin, transparent, enamel-like layer that may be vitrodentine rather than true enamel. Transverse sections of various genera and species of cyathaspids (figs. 100-102) may often be distinguished by differences in the width and shape of the dentine ridges. Ridges are very narrow in Diken- aspis (fig. 101,A) and Listraspis ( mm.), and narrow in Irregulareaspis (fig. 101,B) and Pionaspis ( mm.). They are especially broad in Sanidaspis, Allocryptaspis (fig. 102,C) and Anglaspis (fig. 102,D) ( mm.). The crest of a ridge may be flat, gently rounded, strongly convex, or sharply angular; this character has been used commonly in the systematic revision to dis-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Denison, Robert H. (Robert Howland), 1911-1985; Chicago Natural History Museum. Chicago : Chicago Natural History Museum Press
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